The present invention relates in general to an apparatus and method for the fluid treatment of individual workpieces, such as silicon wafers and the like, by a variety of processing chemicals. More specifically, the present invention is directed to an automated apparatus, in modular form, and method for the chemical treatment by the submersion of the working surface of a silicon wafer in a treating fluid in connection with the manufacture of semiconductor devices therefrom in a manner such that contamination from residual waste chemicals is effectively eliminated during spin drying of the processed wafer.
In the processing of silicon wafers for the manufacture of semiconductor devices therefrom, a number of separate operations must be performed on each wafer. Typically, these operations involve the application of a process chemical to the working surface of the silicon wafer. Different chemicals, for example, acids, bases, developers and solvents, are commonly used in the various chemical operations of wet etching, developing, cleaning, photoresist removal and the like. U.S. Pat. No. 4,281,031 discloses an apparatus for performing a number of such operations on a silicon wafer while it is positioned at a single location or work station. On the other hand, U.S. Pat. No. 4,722,298 discloses a modular processing system which permits the plural arrangement of self-contained processing modules which are independently replaceable as a stand-alone unit with a modular adapted to perform the same or different operation.
In either arrangement, the processing of silicon wafers frequently require that the entire working surface of the wafer be evenly and substantially simultaneously subjected to the treating fluid without impingement on a deposited layer, for example, a photoresist layer. It has been known to submerge silicon wafers either individually or within a cassette of multiple wafers in a bath containing the treating fluid. However, in most circumstances, it is only desired that one surface of the silicon wafer be subjected to the treating fluid, which cannot be achieved by the known submersion techniques. Further, as single silicon wafers are usually processed by mounting to a vacuum chuck, the submersion of the mounted wafer often results in the retention of waste fluids around the chuck even after spin drying. Even a small quantity of retained waste fluid may ultimately contaminate the present and subsequent silicon wafers. In this event, the contaminated silicon wafers are unusable for further processing in the manufacture of semiconductor devices therefrom.
The processing of multiple wafer cassettes also has its disadvantages. For example, all silicon wafers in the cassette must be processed simultaneously, thereby necessitating a large inventory, as well as losing the ability to process silicon wafers individually. The processing of multiple silicon wafers also requires that the entire cassette be submerged and then spun in order to dry the contained wafers. In addition to the difficulty of spinning a large cassette, this spinning cannot assure removal of the waste fluid from each of the silicon wafers, as such waste fluid may accumulate within the interstices of the cassette, further contaminating the present and subsequent wafers.
It can therefore be appreciated that it is desirable during the processing of silicon wafers to ensure that the waste fluid is completely removed to prevent further contamination of wafers being processed. U.S. Pat. No. 4,517,752 discloses an apparatus for continuously draining waste fluids from a silicon wafer in a manner which retards the splashback of fluids upon the wafer during spinning. However, these waste fluids are still prone to collect at a location underlying the silicon wafer surrounding the chuck.